Purification of materials containing fluorides



United States Patent PURIFICATION OF MATERIALS CONTAINING FLUOES LouisSpiegler, Woodbury, N. J.,-assignor to the United States of America asrepresented by the United States Atomic Energy Commission N0 Drawing.Application January 30, 1945, Serial No. 575,353

2 Claims. (Cl. 2314.5)

tions of fluorine in the form of metal fluorides are obtained. Forcertain uses of these uranium compounds the presence of fluorine isobjectionable.

The present invention has for an object the production of uraniumcompounds free from fluorine or having a very low fluorine content. Afurther object of the invention is the production of the black oxide ofuranium, U303, free from metal fluorides. A still further object is theproduction of the black oxide from uranium peroxide containingsubstantial proportions of fluorine.

In accordance with the invention, a uranium compound contaminated withfluorides is heated with aperoxide to a temperature above 350 C. toexpel the fluorine as a volatile fluorine oxide.

The process may be carried out by mixing the uranium compound with ametal peroxide. Thus a black oxide containing fluorine may be mixed withuranium peroxide or another metal peroxide, such as an alkali-metalperoxide, an alkaline earth metal peroxide, or lead peroxide, and themixture may be heated to expel the fluorine in volatile form. It isdesirable that the ratio of peroxide to fluorine suffice to liberate alarge excess of oxygen over the ratio in F20 in order to eliminate thelast traces of fluorine.

Since the use of any metal peroxide other than uranium peroxide entailscontamination of the uranium product with the other metal, it ispreferred to employ uranium peroxide for converting the fluorine to thevolatile fluorine oxide.

In my U. S. patent application Serial No. 559,665, entitled Separationof Uranium from Mixtures, filed October 20, 1944, a process for theisolation of uranium is described involving precipitation of uraniumperoxide from acidic uranyl sulfate solutions. In the manufacture ofsuch solutions from materials containing fluorine, the uranium peroxideproduct is frequently contaminated with a small proportion of fluorinepresent as magnesium fluoride or perhaps a mixed fluoride of two or moremetals. The fluoride impurities present in the product may be eliminatedaccording to the present invention by heating the uranium peroxideproduct to a temperature above 350 Cl, preferably to a temperaturebetween ice The following examples illustrate the process of theinvention.

Example 1 Six samples of uranium peroxide containing from 1.1% to 3.0%of fluorine present as magnesium fluoride were heated in air for twohours at 850 C. This heating converted the uranium peroxide to blackoxide. The fluorine contents of the uranium peroxide and the black oxideproduct are given in the following table.

Percent F Percent F Sample No. by Weight in by weight UO4.2H2O ill U303Each of the uranium peroxide samples was prepared from materialsobtained by a process involving the step of calcining by-producturanium-bearing substances in air at temperatures between 800 C. and1000 C. No fluorine-containing material was added after this calcinationtreatment, which was conducted in the absence of a. peroxide. Thus it isevident that heating in air was not adequate to convert the fluorinepresent to volatile form.

Example 2 A uranium peroxide product obtained in the same manner as thesamples treated in Example 1 contained a weight ratio of fluorine touranium of 0.0061. This product was heated at 800 C. for /2 hour. Theuranium peroxide was converted in this period to black oxide in whichthe weight ratio of fluorine to uranium was 0.0009.

It will be understood that I intend to include variations andmodifications of the invention and that the preceding examples areillustrations only and in no wise to be construed as limitations uponthe invention, the scope of which is defined in the appended claims,wherein:

I claim:

1. The method of reducing the fluorine content of a uranium oxide whichis contaminated with magnesium fluoride impurities which comprisesheating the uranium oxide containing said impurities with uraniumperoxide in the absence of other added reagents to a temperature between500 C. and 1000 C. for a suflicient period of time to expel a major partof the fluorine as a volatile product.

2. The method of producing a uranium oxide of low fluorine content fromprecipitated uranium peroxide which is contaminated with magnesiumfluoride which comprises heating said contaminated uranium peroxide inthe absence of added reagents to a temperature between 500 C. and 1000C. for a suificient period of time to expel a major part of the fluorineas a volatile product.

References Cited in the file of this patent UNITED STATES PATENTS1,634,870 Gerngross July 5, 1927 1,902,832 Caldwell Mar. 28, 19331,994,070 Foss Mar. 12, 1935 OTHER REFERENCES Mellor, Inorganic andTheoretical Chemistry, vol. 2, p. 11, Longmans, London (1932).

Friend, Textbook of Inorganic Chemistry, vol. 7, part 3, p. 311,published in 1926 by Charles Griflin and Co., London.

1. THE METHOD OF REDUCING THE FLUORINE CONTENT OF A URANIUM OXIDE WHICHIS CONTAMINATED WITH MAGNESIUM FLUORIDE IMPURITIES WHICH COMPRISESHEATING THE URANIUM OXIDE CONTAINING SAID IMPURITIES WITH URANIUMPEROXIDE IN THE ABSENCE OF OTHER ADDED REAGENTS TO A TEMPERATURE BETWEEN500* C. AND 1000* C. FOR A SUFFICIENT PERIOD OF TIME OF EXPEL A MAJOR OFTHE FLUORINE AS A VOLATILE PRODUCT.